JP6059639B2 - Toner and method for producing the same - Google Patents

Description

  The present invention relates to a toner and a manufacturing method thereof, and more particularly to a capsule toner and a manufacturing method thereof.

  Patent Document 1 discloses a toner containing hydrophobic silica particles treated with a quaternary ammonium salt compound and having a degree of hydrophobicity of 80% or more.

Japanese Patent Application Laid-Open No. 5-100471

  However, with the toner described in Patent Document 1, it is considered difficult to obtain a toner having excellent charging stability.

  The present invention has been made in view of the above problems, and an object thereof is to provide a toner having excellent charging stability and a method for producing the same. Another object of the present invention is to provide a toner that hardly causes fogging in a formed image and a method for producing the same.

  The toner according to the present invention includes a plurality of toner particles. The toner particles include toner base particles and an external additive added to the surface of the toner base particles. The toner base particles have a core and a shell layer formed on the surface of the core. The external additive has silica particles. The hydrophobicity of the toner base particles is 0% or more and less than 20% (0% ≦ the hydrophobicity of the toner base particles <20%). The degree of hydrophobicity of the external additive is 5% or more and 20% or less (5% ≦ hydrophobic degree of external additive ≦ 20%). The hydrophobicity of the toner base particles is lower than the hydrophobicity of the external additive (the hydrophobicity of the toner base particles <the hydrophobicity of the external additive).

  The method for producing a toner according to the present invention includes a step of forming a core, a step of putting the core and shell layer material in a liquid, and a polymerization reaction of the material of the shell layer in the liquid. Forming a shell layer on the surface to obtain toner base particles having the core and the shell layer; and preparing an external additive having silica particles and having a hydrophobicity of 5% to 20%. And attaching the external additive to the surface of the toner base particles. In the step of obtaining the toner base particles, the formation time of the shell layer by the polymerization reaction is controlled in the range of 30 minutes or more and 90 minutes or less, so that the degree of hydrophobicity of the toner base particles is less than 20%, and , Lower than the hydrophobicity of the external additive.

  According to the present invention, it is possible to provide a toner having excellent charging stability and a method for producing the same. Further, according to the present invention, in addition to this effect or instead of this effect, there may be an effect that it is possible to provide a toner that hardly causes fogging on the formed image and a method for manufacturing the same. .

FIG. 3 is a diagram illustrating toner particles constituting the toner according to the exemplary embodiment of the present invention. It is a figure for demonstrating the method of reading a glass transition point from an endothermic curve. It is a figure for demonstrating the method of reading a softening point from a S-shaped curve. FIG. 10 is a diagram for explaining a method of deteriorating a developer in the evaluation of the fogging amount.

  Hereinafter, embodiments of the present invention will be described.

  The toner according to this embodiment is a capsule toner for developing an electrostatic image. The toner of this embodiment is a powder composed of a large number of particles (hereinafter referred to as toner particles). The toner according to the exemplary embodiment can be used in, for example, an electrophotographic apparatus.

  In an electrophotographic apparatus, an electrostatic image is developed using a developer containing toner. As a result, charged toner adheres to the electrostatic latent image formed on the photoreceptor. After the adhered toner is transferred to the transfer belt, the toner image on the transfer belt is further transferred to a recording medium (for example, paper). Thereafter, the toner is heated and fixed on the recording medium. As a result, an image is formed on the recording medium. For example, a full color image can be formed by superimposing toner images formed using four color toners of black, yellow, magenta, and cyan.

  Hereinafter, the configuration of the toner (particularly toner particles) according to the present embodiment will be described with reference to FIG. FIG. 1 is a view showing toner particles 10 constituting the toner according to the present embodiment.

  As shown in FIG. 1, the toner particle 10 includes a core 11, a shell layer 12 (capsule layer) formed on the surface of the core 11, and an external additive 13.

  The core 11 includes a binder resin 11a and an internal additive 11b (for example, a colorant or a release agent). The core 11 is covered with a shell layer 12. An external additive 13 is attached to the surface of the shell layer 12.

  If not necessary, the internal additive 11b may be omitted. A plurality of shell layers 12 may be formed on the surface of the core 11.

  It is preferable that the core 11 has an anionic property and the shell layer 12 has a cationic property. When the core 11 is anionic, the material of the cationic shell layer 12 can be attracted to the surface of the core 11 when the shell layer 12 is formed. Specifically, for example, the core 11 that is negatively charged in the aqueous medium and the material of the shell layer 12 that is positively charged in the aqueous medium are electrically attracted to each other, and the shell is formed on the surface of the core 11 by, for example, in-situ polymerization. Layer 12 is formed. This makes it easier to form a uniform shell layer 12 on the surface of the core 11 without highly dispersing the core 11 in the aqueous medium using a dispersant.

  In the core 11, the binder resin 11a occupies most of the core component (for example, 85% by mass or more). For this reason, the polarity of the binder resin 11a greatly affects the polarity of the entire core 11. For example, when the binder resin 11a has an ester group, a hydroxyl group, an ether group, an acid group, or a methyl group, the core 11 has a strong tendency to become anionic. For example, the binder resin 11a has an amino group, When it has an amine or amide group, the core 11 has a strong tendency to become cationic.

  In the present embodiment, an indicator that the core 11 is anionic is that the zeta potential of the core 11 measured in an aqueous medium whose pH is adjusted to 4 indicates negative polarity. In order to strengthen the bond between the core 11 and the shell layer 12, it is preferable that the zeta potential of the core 11 at pH 4 is smaller than 0V and the zeta potential of the toner particles 10 at pH 4 is larger than 0V. In the present embodiment, pH 4 corresponds to the pH when the shell layer 12 is formed.

  Examples of the zeta potential measurement method include an electrophoresis method, an ultrasonic method, and an ESA (electroacoustic) method.

  In the electrophoresis method, an electric field is applied to the particle dispersion to cause electrophoresis of charged particles in the dispersion, and the zeta potential is calculated based on the electrophoresis speed. Examples of the electrophoresis method include a laser Doppler method (a method in which an electrophoresis speed is obtained from the amount of Doppler shift of the obtained scattered light by irradiating the electrophoretic particles with laser light). The laser Doppler method has the advantage that the particle concentration in the dispersion does not need to be high, the number of parameters necessary for calculating the zeta potential is small, and the electrophoresis speed can be detected with high sensitivity.

  The ultrasonic method is a method of irradiating a particle dispersion with ultrasonic waves to vibrate charged particles in the dispersion and calculating a zeta potential based on a potential difference caused by the vibration.

  In the ESA method, a high frequency voltage is applied to the particle dispersion to vibrate charged particles in the dispersion to generate ultrasonic waves. Then, the zeta potential is calculated from the magnitude (intensity) of the ultrasonic waves.

  The ultrasonic method and the ESA method have an advantage that the zeta potential can be measured with high sensitivity even in a particle dispersion having a high particle concentration (for example, exceeding 20% by mass).

  Hereinafter, the core 11 (binder resin 11a and internal additive 11b), shell layer 12, and external additive 13 will be described in order.

[core]
The core 11 includes a binder resin 11a and an internal additive 11b. The core 11 includes, for example, a colorant and a release agent as the internal additive 11b. However, unnecessary components (for example, a colorant or a release agent) may be omitted depending on the use of the toner. The core 11 may further include at least one of a charge control agent and magnetic powder as the internal additive 11b.

[Binder resin (core)]
Hereinafter, the binder resin 11a will be described.

  In order to obtain a strong anionic property of the binder resin 11a, the hydroxyl value (OHV value) and the acid value (AV value) of the binder resin 11a are each preferably 10 mgKOH / g or more, more preferably 20 mgKOH / g or more. It is more preferable.

  The glass transition point (Tg) of the binder resin 11a is preferably equal to or lower than the curing start temperature of the thermosetting resin included in the shell layer 12. If such a binder resin 11a is used, sufficient fixability can be easily obtained even during high-speed fixing. Further, the curing start temperature of thermosetting resins (particularly melamine resins) is often about 55 ° C. The Tg of the binder resin 11a is preferably 20 ° C. or higher, more preferably 30 ° C. or higher and 55 ° C. or lower, and further preferably 30 ° C. or higher and 50 ° C. or lower. When the Tg of the binder resin 11a is 20 ° C. or higher, the core 11 is less likely to aggregate when the shell layer 12 is formed.

  The softening point (Tm) of the binder resin 11a is preferably 100 ° C. or less, and more preferably 95 ° C. or less. When the Tm of the binder resin 11a is 100 ° C. or lower (more preferably 95 ° C. or lower), sufficient fixability can be obtained even during high-speed fixing. Further, if the Tm of the binder resin 11a is 100 ° C. or lower (more preferably 95 ° C. or lower), the shell layer 12 is cured during the curing reaction when the shell layer 12 is formed on the surface of the core 11 in an aqueous medium. Since the core 11 is partially softened easily, the core 11 is easily rounded by surface tension. In addition, Tm of the binder resin 11a can be adjusted by combining a plurality of binder resins having different Tm.

  Hereinafter, a method of reading Tg of the binder resin 11a from the endothermic curve will be described with reference to FIG. FIG. 2 is a graph showing an example of an endothermic curve.

  In measuring Tg, an endothermic curve is measured using a differential scanning calorimeter (for example, “DSC-6220” manufactured by Seiko Instruments Inc.). For example, an endothermic curve as shown in FIG. 2 is obtained. The Tg of the binder resin 11a can be obtained from the change point of the specific heat in the endothermic curve of the binder resin 11a.

  Next, a method for reading the Tm of the binder resin 11a from the S-shaped curve will be described with reference to FIG. FIG. 3 is a graph showing an example of an S-shaped curve.

  Tm of the binder resin 11a can be measured using an elevated flow tester (for example, “CFT-500D” manufactured by Shimadzu Corporation). Specifically, the measurement sample is set on an elevated flow tester, and the sample is melted and flowed out under predetermined conditions. Thereby, an S-shaped curve (S-shaped curve related to temperature (° C.) / Stroke (mm)) is obtained. The Tm of the binder resin 11a can be read from the obtained S-shaped curve. In FIG. 3, S1 represents the maximum stroke value, and S2 represents the baseline stroke value on the low temperature side. The temperature at which the stroke value in the S-shaped curve is (S1 + S2) / 2 is defined as Tm of the measurement sample.

The description will be continued with reference to FIG.
As the binder resin 11a, for example, a resin having an ester group, a hydroxyl group, an ether group, an acid group, a methyl group, a carboxyl group, or an amino group as a functional group is preferable. The binder resin 11a is preferably a resin having a functional group such as a hydroxyl group, a carboxyl group, or an amino group in the molecule, and more preferably a resin having a hydroxyl group and / or a carboxyl group in the molecule. The core 11 (binder resin 11a) having such a functional group easily reacts with the material of the shell layer 12 (for example, methylol melamine) and is easily chemically bonded. When such a chemical bond occurs, the bond between the core 11 and the shell layer 12 becomes strong.

  As the binder resin 11a, a thermoplastic resin is preferable.

  Preferred examples of the thermoplastic resin include styrene resin, acrylic resin, styrene acrylic resin, polyethylene resin, polypropylene resin, vinyl chloride resin, polyester resin, polyamide resin, polyurethane resin, and polyvinyl alcohol. Examples thereof include a resin, a vinyl ether resin, an N-vinyl resin, and a styrene-butadiene resin. Among them, the styrene acrylic resin and the polyester resin are excellent in the dispersibility of the colorant in the toner, the charging property of the toner, and the fixing property to the recording medium, respectively.

(Styrene acrylic resin)
Hereinafter, the styrene acrylic resin used as the binder resin 11a will be described.

  The styrene acrylic resin is, for example, a copolymer of a styrene monomer and an acrylic monomer.

  Preferable examples of the styrenic monomer include styrene, α-methylstyrene, p-hydroxystyrene, m-hydroxystyrene, vinyltoluene, α-chlorostyrene, o-chlorostyrene, m-chlorostyrene, p-chloro. Styrene or p-ethylstyrene is mentioned.

  Preferable examples of the acrylic monomer include (meth) acrylic acid, particularly (meth) acrylic acid alkyl ester or (meth) acrylic acid hydroxyalkyl ester. Examples of the (meth) acrylic acid alkyl ester include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, iso-propyl (meth) acrylate, and (meth) acrylic acid n-. Butyl, iso-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, methyl (meth) methacrylate, ethyl (meth) methacrylate, n-butyl (meth) methacrylate, or (meth) Iso-butyl methacrylate is preferred. Examples of (meth) acrylic acid hydroxyalkyl esters include 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, or 4- (meth) acrylic acid 4- Hydroxypropyl is preferred.

  When preparing a styrene acrylic resin, a monomer having a hydroxyl group (for example, p-hydroxystyrene, m-hydroxystyrene, or hydroxyalkyl (meth) acrylate) is used to add a hydroxyl group to the styrene acrylic resin. Can be introduced. For example, the hydroxyl value of the obtained styrene acrylic resin can be adjusted by appropriately adjusting the amount of the monomer having a hydroxyl group.

  When preparing the styrene acrylic resin, a carboxyl group can be introduced into the styrene acrylic resin by using (meth) acrylic acid as a monomer. For example, the acid value of the resulting styrene acrylic resin can be adjusted by appropriately adjusting the amount of (meth) acrylic acid used.

  In order to improve the strength or fixability of the core 11, the number average molecular weight (Mn) of the styrene acrylic resin as the binder resin 11 a is preferably 2000 or more and 3000 or less. The molecular weight distribution of the styrene acrylic resin (ratio Mw / Mn of the mass average molecular weight (Mw) to the number average molecular weight (Mn)) is preferably 10 or more and 20 or less. Gel permeation chromatography can be used for the measurement of Mn and Mw of the binder resin 11a.

(Polyester resin)
Hereinafter, the polyester resin used as the binder resin 11a will be described.

  The polyester resin can be obtained, for example, by polycondensation or copolycondensation of a divalent or trivalent or higher alcohol component and a divalent or trivalent or higher carboxylic acid component.

  Preferable examples of the divalent or trivalent or higher alcohol component include diols, bisphenols, and trivalent or higher alcohols.

  Examples of diols include ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butanediol, neopentyl glycol, 1,4-butenediol, 1,5 -Pentanediol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, dipropylene glycol, polyethylene glycol, polypropylene glycol or polytetramethylene glycol are preferred.

  As the bisphenols, for example, bisphenol A, hydrogenated bisphenol A, polyoxyethylenated bisphenol A, or polyoxypropylenated bisphenol A is preferable.

  Examples of the trivalent or higher alcohols include sorbitol, 1,2,3,6-hexanetetrol, 1,4-sorbitan, pentaerythritol, dipentaerythritol, tripentaerythritol, 1,2,4-butanetriol, 1,2,5-pentanetriol, glycerol, diglycerol, 2-methylpropanetriol, 2-methyl-1,2,4-butanetriol, trimethylolethane, trimethylolpropane, or 1,3,5-trihydroxy Methylbenzene is preferred.

  As the divalent or trivalent or higher carboxylic acid component, for example, an ester-forming derivative (for example, acid halide, acid anhydride, or lower alkyl ester) may be used. Here, “lower alkyl” means an alkyl group having 1 to 6 carbon atoms.

  Examples of the divalent carboxylic acid include maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, phthalic acid, isophthalic acid, terephthalic acid, cyclohexanedicarboxylic acid, succinic acid (for example, alkyl succinic acid or alkenyl succinic acid), Adipic acid, sebacic acid, azelaic acid or malonic acid are preferred. Furthermore, examples of the alkenyl succinic acid include n-butyl succinic acid, n-butenyl succinic acid, isobutyl succinic acid, isobutenyl succinic acid, n-octyl succinic acid, n-octenyl succinic acid, n-dodecyl succinic acid, and n-dodecenyl succinic acid. , Isododecyl succinic acid, or isododecenyl succinic acid.

  Examples of the trivalent or higher carboxylic acid include 1,2,4-benzenetricarboxylic acid (trimellitic acid), 1,2,5-benzenetricarboxylic acid, 2,5,7-naphthalenetricarboxylic acid, 1,2,4. -Naphthalenetricarboxylic acid, 1,2,4-butanetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 1,3-dicarboxyl-2-methyl-2-methylenecarboxypropane, 1,2,4-cyclohexanetricarboxylic acid Acid, tetra (methylenecarboxyl) methane, 1,2,7,8-octanetetracarboxylic acid, pyromellitic acid, or empole trimer acid are preferred.

  When the polyester resin is produced, the acid value and hydroxyl group of the polyester resin are appropriately changed by appropriately changing the amount of the divalent or trivalent or higher alcohol component and the amount of the divalent or trivalent or higher carboxylic acid component. The price can be adjusted. Moreover, when the molecular weight of the polyester resin is increased, the acid value and hydroxyl value of the polyester resin tend to decrease.

  In order to improve the strength or fixability of the core 11, the number average molecular weight (Mn) of the polyester resin as the binder resin 11a is preferably 1200 or more and 2000 or less. The molecular weight distribution (the ratio Mw / Mn of the mass average molecular weight (Mw) to the number average molecular weight (Mn)) of the polyester resin is preferably 9 or more and 20 or less. Gel permeation chromatography can be used for the measurement of Mn and Mw of the binder resin 11a.

[Colorant (core)]
Hereinafter, the colorant (internal additive 11b) will be described.

  As the colorant, for example, a known pigment or dye can be used according to the color of the toner particles 10. The amount of the colorant to be used is preferably 1 part by mass or more and 20 parts by mass or less, and more preferably 3 parts by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the binder resin 11a.

(Black colorant)
The core 11 of the toner particles 10 according to the present embodiment may contain a black colorant. The black colorant is composed of, for example, carbon black. In addition, a colorant that is toned to black using a colorant such as a yellow colorant, a magenta colorant, and a cyan colorant can also be used.

(Coloring agent)
The core 11 of the toner particle 10 according to the present embodiment may contain a color colorant such as a yellow colorant, a magenta colorant, or a cyan colorant.

  The yellow colorant is preferably composed of, for example, a condensed azo compound, an isoindolinone compound, an anthraquinone compound, an azo metal complex, a methine compound, or an allylamide compound. Examples of yellow colorants include C.I. I. Pigment Yellow (3, 12, 13, 14, 15, 17, 62, 74, 83, 93, 94, 95, 97, 109, 110, 111, 120, 127, 128, 129, 147, 151, 154, 155 168, 174, 175, 176, 180, 181, 191 or 194), Neftol Yellow S, Hansa Yellow G, or C.I. I. Butt yellow is preferred.

  The magenta colorant is preferably composed of, for example, a condensed azo compound, diketopyrrolopyrrole compound, anthraquinone compound, quinacridone compound, basic dye lake compound, naphthol compound, benzimidazolone compound, thioindigo compound, or perylene compound. Examples of magenta colorants include C.I. I. Pigment Red (2, 3, 5, 6, 7, 19, 23, 48: 2, 48: 3, 48: 4, 57: 1, 81: 1, 122, 144, 146, 150, 166, 169, 177 184, 185, 202, 206, 220, 221 or 254).

  The cyan colorant is preferably composed of, for example, a copper phthalocyanine compound, a copper phthalocyanine derivative, an anthraquinone compound, or a basic dye lake compound. Examples of cyan colorants include C.I. I. Pigment blue (1, 7, 15, 15: 1, 15: 2, 15: 3, 15: 4, 60, 62, or 66), phthalocyanine blue, C.I. I. Bat Blue, or C.I. I. Acid blue is preferred.

[Release agent (core)]
Hereinafter, the release agent (internal additive 11b) will be described.

  The release agent is used for the purpose of improving the fixing property or offset resistance of the toner. In order to improve the fixing property or the offset resistance, the amount of the release agent used is preferably 1 part by mass or more and 30 parts by mass or less with respect to 100 parts by mass of the binder resin 11a. It is more preferable that the amount is not more than part by mass.

  In one example, the release agent may be composed of an aliphatic hydrocarbon wax such as low molecular weight polyethylene, low molecular weight polypropylene, polyolefin copolymer, polyolefin wax, microcrystalline wax, paraffin wax, or Fischer-Tropsch wax. preferable. In another example, the release agent is preferably composed of an oxide of an aliphatic hydrocarbon wax such as an oxidized polyethylene wax or a block copolymer of oxidized polyethylene wax. In another example, it is preferred that the release agent is composed of a vegetable wax such as candelilla wax, carnauba wax, wood wax, jojoba wax, or rice wax. In another example, the release agent is preferably composed of animal wax such as beeswax, lanolin, or spermaceti. In another example, the release agent is preferably composed of a mineral wax such as ozokerite, ceresin, or vetrolactam. In another example, it is preferable that the mold release agent is composed of waxes based on fatty acid esters such as montanic acid ester wax or caster wax. In another example, it is preferable that the release agent is composed of a wax obtained by deoxidizing a part or all of a fatty acid ester such as deoxidized carnauba wax.

[Charge control agent (core)]
Hereinafter, the charge control agent (internal additive 11b) will be described.

  In the present embodiment, since the core 11 has an anionic property (negative chargeability), a negatively chargeable charge control agent is used in the core 11. The charge control agent is used for the purpose of improving the charge stability or charge rising property and obtaining a toner having excellent durability or stability. The charge rising characteristic is an index as to whether or not the toner can be charged to a predetermined charge level in a short time.

[Magnetic powder (core)]
Hereinafter, the magnetic powder (internal additive 11b) will be described.

  When toner is used as a one-component developer, the amount of magnetic powder used is preferably 35 parts by weight or more and 60 parts by weight or less, and 40 parts by weight or more and 60 parts by weight or less with respect to 100 parts by weight of the total amount of toner. It is more preferable.

  Magnetic powder is made ferromagnetized, for example, iron (ferrite or magnetite), ferromagnetic metal (cobalt or nickel), alloy containing iron and / or ferromagnetic metal, compound containing iron and / or ferromagnetic metal, heat treatment It is preferably composed of a processed ferromagnetic alloy or chromium dioxide.

  The particle size of the magnetic powder is preferably 0.1 μm or more and 1.0 μm or less, and more preferably 0.1 μm or more and 0.5 μm or less. When the particle diameter of the magnetic powder is in such a range, the magnetic powder can be easily dispersed uniformly in the binder resin 11a.

[Shell layer]
As a material of the shell layer 12, a material that is dispersed in water is preferable.

  The shell layer 12 is preferably composed of a thermosetting resin, and more preferably composed of a resin containing a nitrogen atom or a derivative thereof in order to improve strength, hardness, or cationicity. When the shell layer 12 contains nitrogen atoms, the shell layer 12 is easily positively charged. In order to increase the cationic property, the content of nitrogen atoms in the shell layer 12 is preferably 10% by mass or more.

  As the thermosetting resin constituting the shell layer 12, for example, melamine resin, urea (urea) resin, sulfoamide resin, glyoxal resin, guanamine resin, aniline resin, or derivatives of these resins are preferable. As the melamine resin derivative, for example, methylol melamine is preferable. As the guanamine resin derivative, for example, benzoguanamine, acetoguanamine, or spiroguanamine is preferable.

  As the thermosetting resin constituting the shell layer 12, for example, a polyimide resin having a nitrogen element in the molecular skeleton, a maleide polymer, bismuthimide, aminobismuthimide, or bismuthimidetriazine is preferable.

  Examples of the thermosetting resin constituting the shell layer 12 include a resin (hereinafter referred to as an aminoaldehyde resin) produced by polycondensation of a compound containing an amino group and an aldehyde (for example, formaldehyde), or a derivative of an aminoaldehyde resin. Particularly preferred. The melamine resin is a polycondensate of melamine and formaldehyde. Urea resin is a polycondensate of urea and formaldehyde. Glyoxal resin is a polycondensate of a reaction product of glyoxal and urea with formaldehyde.

  Of the resins contained in the shell layer 12, 80% by mass or more of the resin is preferably a thermosetting resin, 90% by mass or more of the resin is more preferably a thermosetting resin, and 100% by mass of the resin is hot. More preferably, it is a cured resin.

  The thickness of the shell layer 12 is preferably 1 nm or more and 20 nm or less, and more preferably 1 nm or more and 10 nm or less.

  When the thickness of the shell layer 12 is 20 nm or less, the shell layer 12 is easily broken by heat and pressure when fixing the toner to the recording medium. As a result, the binder resin 11a and the release agent contained in the core 11 are rapidly softened or melted, and the toner can be fixed on the recording medium in a low temperature range. Further, if the thickness of the shell layer 12 is 20 nm or less, the shell layer 12 is not charged too much, so that an image is properly formed.

  On the other hand, when the thickness of the shell layer 12 is 1 nm or more, the shell layer 12 has sufficient strength, and the destruction of the shell layer 12 due to impact during transportation can be suppressed.

  The thickness of the shell layer 12 can be measured by analyzing a cross-sectional TEM image of the toner particles 10 using commercially available image analysis software (for example, “WinROOF” manufactured by Mitani Corporation).

  In the present embodiment, the shell layer 12 has a cationic property (positive charging property). For this reason, the shell layer 12 may contain a positively chargeable charge control agent.

[External additive]
Hereinafter, the external additive 13 will be described. Hereinafter, the toner particles 10 before being treated with the external additive 13 are referred to as “toner mother particles”.

  The external additive 13 is used to improve the fluidity or handleability of the toner particles 10 and adheres to the surface of the shell layer 12. In order to improve fluidity or handleability, the amount of the external additive 13 used is preferably 0.5 parts by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the toner base particles. More preferably, it is 5 parts by mass or less.

  In order to improve fluidity or handleability, the particle diameter of the external additive 13 is preferably 0.01 μm or more and 1.0 μm or less.

  In the toner according to this embodiment, the toner base particles have a core 11 and a shell layer 12 formed on the surface of the core 11, and the external additive 13 has silica particles. The degree of hydrophobicity of the toner base particles is 0% or more and less than 20% (0% ≦ the degree of hydrophobicity of the toner base particles <20%). The degree of hydrophobicity of the external additive 13 is 5% or more and 20% or less (5% ≦ the degree of hydrophobicity of the external additive 13 ≦ 20%). The hydrophobicity of the toner base particles is lower than the hydrophobicity of the external additive 13 (the hydrophobicity of the toner base particles <the hydrophobicity of the external additive 13).

  The degree of hydrophobicity in the present embodiment (and examples described later) is a value measured by a methanol titration test. Specifically, in the methanol titration test, 0.5 g of toner base particles or 0.05 g of external additive 13 was added to 50 mL of water. Subsequently, while stirring the liquid, titration was performed by dropping methanol with a burette until the total amount of the toner base particles or the external additive 13 in the liquid was wet. The degree of hydrophobicity is a value expressed by volume percentage of the proportion of methanol in the mixture of methanol and water at the end of titration.

  In the toner according to this embodiment, the hydrophobicity of the toner base particles is less than 20%, and the hydrophobicity of the external additive 13 is 5% or more and 20% or less (5% ≦ hydrophobic of the external additive). Degree of conversion ≦ 20%). Covering the surfaces of the toner particles 10 with water (making the toner particles 10 retain water) by lowering the hydrophobicity of the toner base particles and the hydrophobicity of the external additive 13 (making them hydrophilic). Is possible. Further, the surface of the toner particles 10 is covered with an appropriate amount of water by making the degree of hydrophobicity of the external additive 13 not too low (more than 5%). If the surface of the toner particle 10 is covered with an appropriate amount of water, the amount of water on the surface of the toner particle 10 hardly changes even if there is an environmental change (temperature or humidity change). Further, in the toner according to the present embodiment, it is considered that the water adsorption is optimized because the hydrophobicity of the toner base particles is lower than the hydrophobicity of the external additive 13. As a result, it is possible to maintain high chargeability (charge retention characteristics) of the toner particles 10 even when there are environmental fluctuations (temperature or humidity fluctuations). For this reason, the toner according to the exemplary embodiment has excellent charging stability.

  For the toner after external addition, when the hydrophobicity of the toner base particles and the hydrophobicity of the external additive 13 are confirmed, the toner base particles and the external additive 13 can be separated. For example, the toner base particles and the external additive 13 can be separated by an air flow method or a wet method.

  Further, in the toner manufacturing method according to the present embodiment, after the core 11 is formed, the material of the core 11 and the shell layer 12 is put into the liquid. Subsequently, the shell layer 12 is formed on the surface of the core 11 by polymerizing the material of the shell layer 12 in the liquid. Thereby, toner base particles having the core 11 and the shell layer 12 are obtained. Further, an external additive 13 having silica particles and having a hydrophobicity of 5% or more and 20% or less is prepared. Thereafter, the external additive 13 is adhered to the surface of the toner base particles. Further, when forming the toner base particles, the degree of hydrophobicity of the toner base particles is set to less than 20% by controlling the formation time (polymerization time) of the shell layer 12 in the range of 30 minutes to 90 minutes. In addition, the degree of hydrophobicity of the external additive 13 can be lowered. According to such a method, the hydrophobicity of the toner base particles can be easily adjusted to a desired range.

  The silica particles contained in the external additive 13 are preferably hydrophobized hydrophilic silica particles. The external additive 13 may be composed only of hydrophilic silica particles that have been hydrophobized.

  It is preferable that at least a part of hydroxyl groups on the surface of the silica particles contained in the external additive 13 is substituted with alkylsilane or aminosilane. According to such a configuration, it becomes easy to adjust the degree of hydrophobicity of the external additive 13 to 5% or more and 20% or less.

  The difference between the substitution ratio with alkylsilane and the substitution ratio with aminosilane is preferably 0% by mass or more and 5% by mass or less. According to such a configuration, it becomes easy to adjust the degree of hydrophobicity of the external additive 13 to 5% or more and 20% or less.

  In order to improve the storage stability of the toner, the shell layer 12 preferably contains a thermosetting resin. When such a shell layer 12 is formed, it is preferable that the material of the shell layer 12 to be added is a prepolymer or a monomer of a thermosetting resin.

  Table 1 shows toners A to Q evaluated in this example.

  Hereinafter, a preparation method, an evaluation method, and an evaluation result of toners A to Q will be described in order.

[Method for Preparing Toner A]
A method for preparing toner A will be described.

(Production of core)
In the preparation method of the toner A, a low viscosity polyester resin 750 g, a medium viscosity polyester resin 100 g, a high viscosity polyester resin 150 g, and a release agent 55 g using a mixer (“Henschel mixer” manufactured by Nippon Coke Industries, Ltd.). And 40 g of the colorant were mixed at a rotational speed of 2400 rpm. By increasing the ratio of the low-viscosity polyester resin in the binder resin 11a (polyester resin), the melt viscosity of the binder resin 11a can be lowered.

  In the low viscosity polyester resin, Tg is 38 ° C. and Tm is 65 ° C. In the medium viscosity polyester resin, Tg is 53 ° C. and Tm is 84 ° C. In the high viscosity polyester resin, Tg is 71 ° C. and Tm is 120 ° C.

  As a colorant, “KET Blue 111” (phthalocyanine blue) manufactured by DIC Corporation was used. As the release agent, “Carnauba Wax No. 1” manufactured by Hiroyuki Kato Co., Ltd. was used.

  Subsequently, the obtained mixture was mixed using a biaxial extruder (“PCM-30” manufactured by Ikegai Co., Ltd.) with a material input amount of 5 kg / hour, a shaft rotation speed of 160 rpm, and a set temperature range of 100 ° C. to 130 ° C. It was melt-kneaded under conditions. Thereafter, the obtained melt-kneaded product was cooled.

  Subsequently, the melt-kneaded material was roughly pulverized using a mechanical pulverizer (“Rotoplex 16/8 type” manufactured by Toa Machinery Co., Ltd.). Further, the coarsely pulverized product was finely pulverized using a jet mill (“Ultrasonic Jet Mill I Type” manufactured by Nippon Pneumatic Industry Co., Ltd.). Subsequently, the finely pulverized product was classified using a classifier (“Elbow Jet EJ-LABO type” manufactured by Nippon Steel Mining Co., Ltd.). As a result, a core 11 having a median diameter (volume distribution standard) of 6.0 μm was obtained. The core 11 was anionic.

(Formation of shell layer)
A 1 L three-necked flask equipped with a thermometer and a stirring blade was prepared, and 500 mL of ion-exchanged water and sodium polyacrylate (“Jurimer (registered trademark) AC-103” manufactured by Toagosei Co., Ltd.) were prepared in the flask. 50 g was added. Thereby, the sodium polyacrylate aqueous solution was obtained in the flask.

  Subsequently, 100 g of the core 11 (powder) prepared by the above-described procedure was added to the sodium polyacrylate aqueous solution. Thereafter, the contents of the flask were sufficiently stirred at room temperature. Thereby, the dispersion liquid of the core 11 was obtained in the flask.

  Subsequently, the dispersion liquid of the core 11 was filtered using a filter paper having an opening of 3 μm. Thereby, the core 11 was separated by filtration. Subsequently, the core 11 was redispersed in ion exchange water. Thereafter, the core 11 was washed by repeating filtration and redispersion five times. Subsequently, a suspension in which 100 g of the core 11 was dispersed in 500 mL of ion exchange water was prepared in the flask.

  Subsequently, 1 g of methylolated urea (“Milben Resin SU-100 (solid content concentration 80%)” manufactured by Showa Denko KK)) was added to the flask, and the contents of the flask were stirred to dissolve methylolated urea in the suspension. I let you. Subsequently, dilute hydrochloric acid was added to the flask to adjust the pH of the suspension in the flask to 4.

  Subsequently, the suspension was transferred to a 1 L separable flask. Subsequently, the contents of the flask were heated with stirring (the temperature in the flask was raised to 65 ° C.), and the state at 65 ° C. was maintained for 60 minutes with stirring. Thereby, the core 11 and the material of the shell layer 12 polymerized in the flask, and the cationic shell layer 12 composed of a thermosetting resin (urea resin) was formed on the surface of the core 11. As a result, a dispersion containing toner mother particles was obtained.

(Washing and drying)
The dispersion of the toner base particles (core 11 and shell layer 12) was filtered (solid-liquid separation) to obtain toner base particles. Thereafter, the toner base particles were redispersed in ion exchange water. Further, the toner base particles were washed by repeating dispersion and filtration. Thereafter, the toner base particles were dried. Since washing (dispersion and filtration) was repeated, almost no dispersant (sodium polyacrylate) remained inside and on the surface of the toner base particles. The toner mother particles thus obtained had a hydrophobicity of 5%.

(External)
The external additive 13 was produced by hydrophobizing hydrophilic silica. As the hydrophilic silica, hydrophilic fumed silica having a BET specific surface area of 130 m ² / g (“AEROSIL (registered trademark) 130” manufactured by Nippon Aerosil Co., Ltd.) was used.

  As the hydrophobization treatment, the hydroxyl group on the surface of hydrophilic silica was substituted with alkylsilane at a substitution ratio of 30% by mass, and the hydroxyl group on the surface of hydrophilic silica was substituted with aminosilane at a substitution ratio of 30% by mass. As the alkylsilane, polyethylene oxide-containing alkoxysilane (“A-1230” manufactured by Nihon Unicar Co., Ltd.) was used. As aminosilane, 3-aminopropyltriethoxysilane (“KBE-903” manufactured by Shin-Etsu Chemical Co., Ltd.) was used. The degree of hydrophobicity of the obtained external additive 13 was 10%.

  Subsequently, the external additive 13 (hydrophilic silica subjected to the hydrophobization treatment) was mixed at a ratio of 1.5% by mass with respect to the dried toner base particles. As a result, a toner A having a large number of toner particles 10 was obtained.

[Method for Preparing Toner B]
The preparation method of the toner B relates to the hydrophobization treatment of the external additive 13 except that the substitution ratio of alkylsilane is changed from 30% by mass to 40% by mass and the substitution ratio of aminosilane is changed from 30% by mass to 40% by mass. Is substantially the same as the method for preparing toner A. The hydrophobicity of the external additive 13 used for the preparation of the toner B was 18%, and the hydrophobicity of the toner base particles was 5%.

[Method for Preparing Toner C]
The preparation method of the toner C is the preparation of the toner A except that the stirring temperature is changed from 65 ° C. to 60 ° C. and the stirring time is changed from 60 minutes to 30 minutes with respect to the conditions (encapsulation conditions) for forming the shell layer 12. It is almost the same as the method. The hydrophobicity of the external additive 13 used for the preparation of the toner C was 10%, and the hydrophobicity of the toner base particles was 2%.

[Method for Preparing Toner D]
The preparation method of toner D is the preparation of toner B except that the stirring temperature is changed from 65 ° C. to 70 ° C. and the stirring time is changed from 60 minutes to 90 minutes with respect to the conditions (encapsulation conditions) for forming the shell layer 12. It is almost the same as the method. The degree of hydrophobicity of the external additive 13 used in the preparation of the toner D was 18%, and the degree of hydrophobicity of the toner base particles was 15%.

[Method for Preparing Toner E]
The preparation method of the toner E relates to the hydrophobization treatment of the external additive 13 except that the substitution ratio of alkylsilane is changed from 30% by mass to 25% by mass and the substitution ratio of aminosilane is changed from 30% by mass to 25% by mass. Is substantially the same as the method for preparing toner C. The hydrophobicity of the external additive 13 used for the preparation of the toner E was 6%, and the hydrophobicity of the toner base particles was 2%.

[Method for Preparing Toner F]
The preparation method of the toner F is substantially the same as the preparation method of the toner D except that the aminosilane substitution ratio is changed from 40% by mass to 45% by mass with respect to the hydrophobization treatment of the external additive 13. The hydrophobicity of the external additive 13 used for the preparation of the toner F was 20%, and the hydrophobicity of the toner base particles was 15%.

[Method for Preparing Toner G]
Toner G was prepared by using methylol melamine (“Nikaresin S-176 (solid content concentration: 80%)” manufactured by Nippon Carbide Industries, Ltd.) instead of methylol urea (“Milben Resin SU-100” manufactured by Showa Denko KK). Except for the use, it is almost the same as the preparation method of the toner A. The addition amount of methylol melamine (“Nika Resin S-176” manufactured by Nippon Carbide Industries Co., Ltd.) was 1 g. The hydrophobicity of the external additive 13 used for the preparation of the toner G was 10%, and the hydrophobicity of the toner base particles was 5%.

[Method for Preparing Toner H]
Toner H was prepared by using methylol melamine (“Nikaresin S-260 (solid content concentration: 80%)” manufactured by Nippon Carbide Industries Co., Ltd.) instead of methylolated urea (“Milben Resin SU-100” manufactured by Showa Denko KK). Except for the use, it is almost the same as the preparation method of the toner A. The addition amount of methylol melamine (“Nika Resin S-260” manufactured by Nippon Carbide Industries Co., Ltd.) was 1 g. The hydrophobicity of the external additive 13 used for the preparation of the toner H was 10%, and the hydrophobicity of the toner base particles was 5%.

[Method for Preparing Toner I]
The toner I was prepared by preparing toner E except that the stirring temperature was changed from 60 ° C. to 65 ° C. and the stirring time was changed from 30 minutes to 75 minutes with respect to the conditions (encapsulation conditions) for forming the shell layer 12. It is almost the same as the method. The hydrophobicity of the external additive 13 used for the preparation of the toner I was 10%, and the hydrophobicity of the toner base particles was 10%.

[Method for Preparing Toner J]
The toner J was prepared in the same manner as the toner A except that the stirring temperature was changed from 65 ° C. to 70 ° C. and the stirring time was changed from 60 minutes to 120 minutes. It is almost the same as the method. The hydrophobicity of the external additive 13 used for the preparation of the toner J was 10%, and the hydrophobicity of the toner base particles was 22%.

[Method for Preparing Toner K]
The preparation method of the toner K relates to the hydrophobization treatment of the external additive 13 except that the alkylsilane substitution ratio is changed from 25 mass% to 45 mass% and the aminosilane substitution ratio is changed from 25 mass% to 45 mass%. Is substantially the same as the method for preparing toner I. The hydrophobicity of the external additive 13 used for the preparation of the toner K was 23%, and the hydrophobicity of the toner base particles was 10%.

[Method for Preparing Toner L]
The preparation method of the toner L is substantially the same as the preparation method of the toner A except that the following conditions are changed.

  In the toner L preparation method, regarding the hydrophobization treatment of the external additive 13, the alkylsilane substitution ratio was changed from 30 mass% to 50 mass%, and the aminosilane substitution ratio was changed from 30 mass% to 50 mass%. Moreover, regarding the conditions (encapsulation conditions) for forming the shell layer 12, the stirring temperature was changed from 65 ° C to 75 ° C, and the stirring time was changed from 60 minutes to 120 minutes. The hydrophobicity of the external additive 13 used for the preparation of the toner L was 25%, and the hydrophobicity of the toner base particles was 24%.

[Method for Preparing Toner M]
The preparation method of the toner M relates to the hydrophobization treatment of the external additive 13 except that the substitution ratio of alkylsilane is changed from 30% by mass to 20% by mass and the substitution ratio of aminosilane is changed from 30% by mass to 20% by mass. Is substantially the same as the method for preparing toner A. The hydrophobicity of the external additive 13 used for the preparation of the toner M was 2%, and the hydrophobicity of the toner base particles was 5%.

[Method for Preparing Toner N]
The method for preparing the toner N is substantially the same as the method for preparing the toner A except that the stirring time is changed from 60 minutes to 120 minutes with respect to the conditions (encapsulation conditions) for forming the shell layer 12. The hydrophobicity of the external additive 13 used for the preparation of the toner N was 10%, and the hydrophobicity of the toner base particles was 20%.

[Method for Preparing Toner O]
The toner O was prepared by using methylol melamine (“Nikaresin S-176 (solid content concentration: 80%)” manufactured by Nippon Carbide Industries, Ltd.) instead of methylolated urea (“Milben Resin SU-100” manufactured by Showa Denko KK). Except for the use, it is almost the same as the preparation method of the toner I. The addition amount of methylol melamine (“Nika Resin S-176” manufactured by Nippon Carbide Industries Co., Ltd.) was 1 g. The hydrophobicity of the external additive 13 used for the preparation of the toner O was 6%, and the hydrophobicity of the toner base particles was 10%.

[Method for Preparing Toner P]
The toner P was prepared by using methylol melamine (“Nikaresin S-260 (solid content concentration: 80%)” manufactured by Nippon Carbide Industries, Ltd.) instead of methylolated urea (“Milben Resin SU-100” manufactured by Showa Denko KK). Except for the use, it is almost the same as the preparation method of the toner I. The addition amount of methylol melamine (“Nika Resin S-260” manufactured by Nippon Carbide Industries Co., Ltd.) was 1 g. The degree of hydrophobicity of the external additive 13 used for the preparation of the toner P was 6%, and the degree of hydrophobicity of the toner base particles was 11%.

[Method for Preparing Toner Q]
The preparation method of the toner Q is substantially the same as the preparation method of the toner F except that the substitution ratio of the alkylsilane is changed from 40% by mass to 35% by mass with respect to the hydrophobization treatment of the external additive 13. The hydrophobicity of the external additive 13 used for the preparation of the toner Q was 22%, and the hydrophobicity of the toner base particles was 15%.

[Evaluation method]
The evaluation method of each sample (toners A to Q) is as follows.

(Charge amount)
A carrier (“carrier for FS-C5300DN” manufactured by Kyocera Document Solutions Co., Ltd.) and a sample (toner) of 10% by mass with respect to the mass of the carrier were mixed using a ball mill. Thereby, a developer for evaluation was obtained.

  Subsequently, an evaluation developer (hereinafter referred to as a first evaluation developer) left for 24 hours in an environment of a temperature of 20 ° C. and a humidity of 65% RH, and an environment of a temperature of 35 ° C. and a humidity of 80% RH. And a developer for evaluation (hereinafter referred to as a second developer for evaluation) and a developer for evaluation (hereinafter referred to as a third developer) left for 24 hours in an environment of a temperature of 10 ° C. and a humidity of 10% RH. The amount of charge was measured for each of the evaluation developers. For the measurement of the charge amount, a suction-type small charge amount measuring device (“Model 212HS” manufactured by Trek Japan Co., Ltd.) was used.

  For any of the first evaluation developer, the second evaluation developer, and the third evaluation developer, “good (good)” if the charge amount is 10 μC / g or more and 30 μC / g or less. If it was less than 10 μC / g or more than 30 μC / g, it was evaluated as “x (not good)”.

(Cover amount)
In a 100 cc plastic container, 100 g of a carrier (“carrier for FS-C5300DN” manufactured by Kyocera Document Solutions Co., Ltd.) and a sample (toner) of 6% by mass with respect to the mass of the carrier are placed. The carrier and the toner were stirred for 10 minutes using “Rocking Mixer (registered trademark)” manufactured by Aichi Electric Co., Ltd. Subsequently, the mixture (developer) in the plastic container was deteriorated.

  Hereinafter, a method of deteriorating the developer will be described mainly with reference to FIG. FIG. 4 is a view showing a deterioration jig 100 used for deteriorating the developer.

  As shown in FIG. 4, the deterioration jig 100 includes a rotation drive unit 101 (for example, a motor), a rotation shaft 101a, a plate 102, and a tray 103. The rotation drive unit 101 rotates the rotation shaft 101a. The plate 102 rotates integrally with the rotary shaft 101a. The plate 102 has a protrusion 102a (blade). The saucer 103 was an approximately 100 cc aluminum dish.

  The radius R of the saucer 103 was 28 mm. The depth D1 of the saucer 103 was 25 mm. The distance D2 between the bottom surface of the tray 103 and the protrusion 102a of the plate 102 was 1 mm. A distance D3 between the bottom surface of the tray 103 and the top surface of the carrier was 5 mm. The distance L1 between the side surface of the tray 103 and the protrusion 102a of the plate 102 was 3 mm. The width L2 of the protrusion 102a of the plate 102 was 20 mm.

  The mixture (developer S) in the plastic container was placed in the receiving tray 103. Then, the developer S was stirred for 10 minutes by rotating the rotating shaft 101a (and thus the plate 102) by the rotation driving unit 101. As a result, the developer S was sandwiched between the tray 103 and the protrusion 102a, and the developer S deteriorated. As a result, a deteriorated developer was obtained.

  Subsequently, 3 g of the deteriorated developer was put in a 20 cc bottle, and 0.18 g of a sample (undegraded toner) was further added. Subsequently, the contents of the bottle were stirred for 1 minute using a powder mixer (“Rocking Mixer (registered trademark)” manufactured by Aichi Electric Co., Ltd.). Thereby, a developer for evaluation was obtained.

  2 g of developer for evaluation was uniformly placed on a SUS304 sleeve (230 mm in length, 20 mm in diameter) having a magnet inside, and electrodes (upper and lower divided electrodes) were set on the sleeve at a distance of 4.5 mm. Then, while rotating the sleeve, a voltage of 1.5 kV was applied to the electrode for 30 seconds, and the amount of flying toner (reversely charged toner) adhering to the electrode was measured as the fogging amount.

  When the amount of flying toner was less than 20 mmg, it was evaluated as “◯ (good)”, and when it was 20 mmg or more, it was evaluated as “x (not good)”.

[Evaluation results]
Table 2 summarizes the results of evaluating the charge amount and the fog amount of the toners A to Q.

  In toners A to H and J, the charge amounts of the first evaluation developer, the second evaluation developer, and the third evaluation developer were 10 μC / g or more and 30 μC / g or less, respectively. .

  For toners I, M, O, and P, the charge amount of the second evaluation developer was less than 10 μC / g.

  For toners K, N, and Q, the charge amount of the third evaluation developer was more than 30 μC / g.

  In the toner L, the charge amount of each of the first evaluation developer and the third evaluation developer was more than 30 μC / g.

  For toners A to I, K, L, N, O, and Q, the amount of flying toner (fogging amount) was less than 20 mmg.

  In each of toners J, M, and P, the amount of flying toner (fogging amount) was 20 mmg or more.

  As described above, in toners A to H, the hydrophobicity of the toner base particles was 0% or more and less than 20% (see Table 1). The degree of hydrophobicity of the external additive 13 was 5% or more and 20% or less (see Table 1). Further, the hydrophobicity of the toner base particles was lower than the hydrophobicity of the external additive 13 (see Table 1). The toners A to H having such a configuration had excellent charging stability (see Table 2). Further, when an image was formed using toners A to H, the formed image was hardly fogged (see Table 2).

  In the method for preparing toners A to H, after the core 11 was formed, the core 11 and the material of the shell layer 12 were put into the liquid. Subsequently, the shell layer 12 was formed on the surface of the core 11 by polymerizing the material of the shell layer 12 in the liquid. As a result, toner base particles having a core 11 and a shell layer 12 were obtained. Further, an external additive 13 having silica particles and having a hydrophobicity of 5% to 20% was prepared. Thereafter, the external additive 13 was adhered to the surface of the toner base particles. Further, when forming the toner base particles, the formation time (polymerization time) of the shell layer 12 was controlled in the range of 30 minutes to 90 minutes (see Table 1). As a result, the degree of hydrophobicity of the toner base particles was made less than 20% and lower than the degree of hydrophobicity of the external additive 13. By such a method, the hydrophobicity of the toner base particles could be easily adjusted to a desired range.

  In toners A to H, the difference between the substitution ratio with alkylsilane and the substitution ratio with aminosilane was 0% by mass or more and 5% by mass or less. Specifically, in toners A to E, G, and H, the substitution ratio with alkylsilane and the substitution ratio with aminosilane were the same, and the difference between them was 0% by mass. In toner F, the difference between the substitution ratio with alkylsilane and the substitution ratio with aminosilane was 5 mass% (= 45 mass% -40 mass%).

  In each of the toners A to H, the shell layer 12 was substantially composed of only a thermosetting resin. In each of the preparation methods of the toners A to H, a prepolymer of a thermosetting resin was added as a material for the shell layer 12.

The present invention is not limited to the above embodiments.
In the toner, the hydrophobicity of the toner base particles is from 0% to less than 20%, the hydrophobicity of the external additive having silica particles is from 5% to 20%, and the hydrophobicity of the toner base particles is outside. When it is lower than the hydrophobicity of the additive, the toner has excellent charging stability.

  Further, when the toner base particles are produced, the formation time (polymerization time) of the shell layer 12 is controlled in the range of 30 minutes or more and 90 minutes or less, so that the degree of hydrophobicity of the toner base particles is less than 20%. In addition, when the degree of hydrophobicity of the external additive having silica particles is set lower than 5% or more and 20% or less, it becomes easy to adjust the degree of hydrophobicity of the toner base particles to a desired range.

  The toner according to the present invention can be used for forming an image in, for example, a copying machine or a printer.

DESCRIPTION OF SYMBOLS 10 Toner particle 11 Core 11a Binder resin 11b Internal additive 12 Shell layer 13 External additive

Claims (2)

A toner comprising a plurality of toner particles,
The toner particles include toner base particles and an external additive added to the surface of the toner base particles.
The toner base particles have a core and a shell layer formed on the surface of the core,
The shell layer includes urea resin or melamine resin,
The external additive has silica particles,
At least a part of hydroxyl groups on the surface of the silica particles is substituted with alkylsilane or aminosilane,
The hydrophobicity of the toner base particles is 0% or more and less than 20%,
The hydrophobicity of the external additive is 5% or more and 20% or less,
The hydrophobicity of the toner base particles rather lower than hydrophobicity of the external additive,
The difference between the substitution ratio with the alkylsilane and the substitution ratio with the aminosilane is 0% by mass or more and 5% by mass or less . Forming a core;
Placing the core and shell layer material in a liquid;
A step of polymerizing the material of the shell layer in the liquid to form the shell layer on the surface of the core to obtain toner mother particles having the core and the shell layer;
Providing an external additive having silica particles and having a degree of hydrophobicity of 5% or more and 20% or less;
Attaching the external additive to the surface of the toner base particles;
Including
The material of the shell layer is a prepolymer or a monomer that forms a urea resin or a melamine resin,
In the step of obtaining the toner base particles, the formation time of the shell layer by the polymerization reaction is controlled in the range of 30 minutes or more and 90 minutes or less, so that the degree of hydrophobicity of the toner base particles is less than 20%, and , Lower than the hydrophobicity of the external additive,
In the step of preparing the external additive, at least a part of hydroxyl groups on the surface of the silica particles is substituted with alkylsilane or aminosilane ,
The toner production method, wherein a difference between the substitution ratio with the alkylsilane and the substitution ratio with the aminosilane is 0% by mass or more and 5% by mass or less .

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